This application claims the benefit of Japanese Patent Application Number 2005-287673 filed on Sep. 30, 2005, the entirety of which is incorporated by reference.
1. Field of the Invention
The present invention relates to a cover structure for covering a cutting space in a machine tool.
2. Description of the Related Art
Conventionally, a cutting space 52 of a machine tool 51 is covered with a cover 53 as shown in FIG. 4. The cover 53 has an opening portion 55 which is opened and closed by a slide door 56. When the door 56 is slid to open the opening portion 55, a tool exchange device 57 rotates an exchange arm 58 for inserting the exchange arm 58 into the cutting space 52 through the opening portion 55, and exchanges tools (not shown) attached to a main spindle 54 of the machine tool 51.
Another cover structure of a machine tool is proposed as disclosed in Japanese unexamined patent publication No. 09-309044, where a plurality of doors are used to open and close an opening portion defined in a cover. This cover structure of the machine tool is explained based on FIG. 5, which shows an explanatory cross-sectional plain view.
In this cover structure of the machine tool, an opening portion 64 which is V-shaped in a plain view is defined on a cover 63 which covers a cutting space 62. As a door for opening and closing the opening portion 64, a first door 65 which is V-shaped in a plain view and a small-sized second door 66 are mounted. The first door 65 is slidable along a guide axis 67 and the second door 66 is pivotable around a vertical axis 68. With this configuration, the first door 65 and the second door 66 are synchronized to open and close the opening portion 64 by means of a door opening/closing mechanism 72 including a drive shaft 69, a sector gear 70, and a sprocket wheel 71, etc.
However, in the structure as shown in FIG. 4, because a frontage of the opening portion is opened and closed by a single door, it is necessary to have a longer stroke of opening and closing the door. Consequently, it takes time to open and close the door, which would be an obstacle to a quick working.
On the other hand, in the structure disclosed in Japanese unexamined patent publication No. 09-309044, since a plurality of doors are used upon opening and closing the opening portion, each opening and closing stroke of the door can be shortened. However, the door opening/closing mechanism becomes complex as described above, so that a higher cost is required as the cost of equipment, etc. Moreover, the overall equipment needs to be enlarged because space for installing the door opening/closing mechanism is required.
Moreover, in a conventional structure as shown in FIGS. 4 and 5, a portion which needs not to be open (for example, a portion except a tool passing portion, such as an upper or lower portion of the opening portion, and a portion on the axis line of the exchange arm) is made to be open as the opening portion. In other words, the opening portion has a broad area which is unnecessary to be opened and closed. As a result, there are problems of waste of time, deterioration of work efficiency, and so on. Further, even if the opening portion is made to be open only at the time of tool exchange, there is a problem that cutting dust or cutting fluid used in working, etc. easily disperses outside the cutting space as long as an opening area is broad.
In view of the above, an object of the present invention is to provide a cover structure of a machine tool with a simple structure which improves work efficiency by minimizing an opening portion.